People around the world have been watching, wringing their hands over – and even praying for – the fourth peregrine falcon egg atop San Jose City Hall that hasn’t hatched yet, even though its three siblings were born healthy and hungry last week.

The lead scientist studying these birds has a theory about why the unhatched egg may be a dud.

Seems that Papa Bird may have been shooting blanks.

“Here’s what I think,” said Glenn Stewart, coordinator of the University of California’s Santa Cruz Predatory Bird Research Group, which has been monitoring the falcons’ behavior. “I think it was likely he was not producing viable semen in the initial contact.”

So the “fourth egg” everyone’s talking about – on a message group with 1,600 people from Florida to Finland – isn’t really the fourth egg at all. Stewart suspects it was the first egg, which Carlos simply wasn’t able to fertilize.

The eggs were laid in March, and three of them hatched April 22.

In the last 48 hours before the egg is laid, a shell forms. Baby falcons incubate for 33 days before hatching.

Peregrine falcons have made a strong comeback in California – thanks, in part, to rescue efforts. In the 1970s, there were only two known pairs of peregrines; today, there are likely at least 250 pairs of this type of falcon statewide.

Stewart and his team will know more – including the gender of the three baby falcons – in mid-May, when the scientists put bands on the falcons’ legs to track them after they’ve flown off to the wild. The young falcons should begin to fly in six weeks.

For now, the birds are cozy on the south ledge of City Hall, eating bird meat their mother catches in the sky and rips into little pieces to feed them. And, like human babies, they’re spending time sleeping, pooping and growing quickly. Stewart said the falcons seem four times bigger today than they did when they were born.

Stewart’s hypothesis about the unhatched egg has quieted some of the discussion on the electronic message board set up about the falcons, said Evet Loewen, who works at City Hall and has volunteered to monitor the forum.

When will it hatch? Why is it taking so long? Some people, Loewen said, even said they were going to pray for it.

“We were all sitting around talking about the fourth egg, the fourth egg,” she said. “But nobody was thinking that this was the practice egg.”

IF YOU’RE INTERESTED

To watch Clara, Carlos and their offspring, go to www.sanjoseca.gov and click on the Falcon Cam link. To join the falcon discussion forum at the Santa Cruz Predatory Bird Research Group’s Web site at www.scpbrg.org, click on Nest Cameras, select the San Jose camera and go to the discussion forum link.